// JavaScript Document
(function ($) {
    var goToTopTime;
    $.fn.goToTop = function (options) {
        var opts = $.extend({}, $.fn.goToTop.def, options);
        var $window = $(window);
        $body = (window.opera) ? (document.compatMode == "CSS1Compat" ? $('html') : $('body')) : $('html,body'); // opera fix
        $(this).hide();
        var $this = $(this);
        clearTimeout(goToTopTime);
        goToTopTime = setTimeout(function () {
            var controlLeft;
            if ($window.width() > opts.pageHeightJg * 2 + opts.pageWidth) {
                controlLeft = ($window.width() - opts.pageWidth) / 2 + opts.pageWidth + opts.pageWidthJg;
            } else {
                controlLeft = $window.width() - opts.pageWidthJg - $this.width();
            }
            var cssfixedsupport = $.browser.msie && parseFloat($.browser.version) < 7; //判断是否ie6
            var controlTop = $window.height() - $this.height() - opts.pageHeightJg;
            controlTop = cssfixedsupport ? $window.scrollTop() + controlTop : controlTop;
            var shouldvisible = ($window.scrollTop() >= opts.startline) ? true : false;

            if (shouldvisible) {
                $this.stop().show(opts.showBtntime);
            } else {
                $this.stop().hide(opts.showBtntime);
            }

            $this.css({
                position: cssfixedsupport ? 'absolute' : 'fixed',
                top: controlTop,
                left: controlLeft
            });
        }, 500);

        $(this).click(function (event) {
            $body.stop().animate({ scrollTop: $(opts.targetObg).offset().top }, opts.duration);
            $(this).blur();
            event.preventDefault();
            event.stopPropagation();
        });
    };

    $.fn.goToTop.def = {
        pageWidth: 950, //页面宽度
        pageWidthJg: 10, //按钮和页面的间隔距离
        pageHeightJg: 50, //按钮和页面底部的间隔距离
        startline: 20, //出现回到顶部按钮的滚动条scrollTop距离
        duration: 200, //回到顶部的速度时间
        showBtntime: 100, //显示\隐藏回到顶部按钮的速度时间
        targetObg: "body"//目标位置
    };
})(jQuery);
$(function () {
    $('<a href="#" class="go-top"><img src="http://css.sodao.com/home/img/goToTop.png" alt="" /></a>').appendTo("body");
});
